PARIS, March 9 (Reuters) - Shares in Lagardere, the French media group behind Paris Match and Europe 1 radio, slumped on Friday as investors reacted to a weak increase in 2017 net income and disappointing guidance for the year ahead.

Lagardere shares traded down 6.4 percent early in the session, among the worst performers on Paris' SBF-120 index and on the pan-European STOXX 600 index.

Lagardere's results were the latest in a relatively weak set of updates from media companies in the face of possible advertising cuts by major clients.

Earlier this week, shares in German publisher Axel Springer fell more heavily after weaker-than-expected results.

Lagardere forecast that its 2018 operating profits would be flat compared with 2017, as it posted a slight rise in full-year earnings.

Its 2017 net income edged up to 179 million euros ($220.38 million) from 175 million euros a year earlier, coming in below analysts' forecasts.

Its free cash flow also fell 39 percent to 283 million euros, which Lagardere said reflected higher working capital costs and less of a boost from property sales compared to the year before.

Bank of America Merrill Lynch kept an "underperform" rating on Lagardere, citing an "underwhelming guidance and weak free cash flow" as negative factors in its results.

That view was echoed by Barclays, which maintained an "equal weight" rating on Lagardere shares.

"2017 was in line at the EBITA (earnings before interest, tax and amortisation) level, but below at net income. 2018 estimated guidance is as expected and 2017 cash flow was poor," wrote Barclays.

On Thursday, company head Arnaud Lagardere did not rule out selling magazine brand Elle, but dismissed the possible sale of its weekly newspaper Paris Match and radio Europe 1.